Technical Abstract:
Verticillium wilt is a serious yield-limiting factor for potato production worldwide. The disease is caused mainly by the soil-borne fungus V. dahliae. Cultural practices provide limited control of the disease. Fumigation is effective but costly. Host plant resistance, however, offers an attractive alternative for reducing the impact of Verticillium wilt in potato production. High levels of Verticillium wilt resistance have been identified in wild Solanum species and their hybrids with the cultivated potato. A reliable screening assay is necessary to identify resistant clones in screening, breeding, and genetics studies. Symptom expression is typically not an effective screening strategy in segregating populations because the “early dying” symptoms of the disease can be confused with natural senescence. Stem colonization assays are preferred and typically involve the plating of stem sap or dried stems, followed by incubation and colony counting. However, these assays are time-consuming and can produce ambiguous results. A quantitative PCR assay that overcomes these limitations has been developed. In addition, techniques are being evaluated to identify Verticillium wilt resistance in early generations of a breeding program. These efforts should lead to the development of potato varieties with improved Verticillium wilt resistance.